When an aluminum or aluminum alloy wire is crimped in a crimping sleeve, and given the difference in the thermal expansion coefficients of aluminum and the metal constituting the crimping sleeve, which is often a copper alloy, alumina is formed around the wire by oxidation in air. Unfortunately, alumina is electrically resistive and consequently leads to an increase in electrical contact resistance, which can lead to contact being broken, when conveying light currents, or else to overheating, when conveying heavy currents.